1. Field of the Invention
This invention generally relates to an underfloor cable distribution system for a building and, more particularly, to increasing the capacity of a trench employed to feed electrical cables to the system.
2. Description of Related Art
A variety of underfloor cable distribution systems have been proposed in the art. See, for example, U.S. Pat. Nos. 3,721,051; 3,426,802 and 3,453,791. Also, see my own U.S. Pat. Nos. 4,558,546; 4,559,749; 4,580,379 and 4,625,480.
As described in my previous patents, it is known for the construction of an "electrified floor" to lay a plurality of longitudinally-extending, corrugated, metal flooring units side by side with a plurality of longitudinally-extending, metal, cable distribution ducts. The flooring units and the distribution ducts are supported by structural floor beams. A plurality of trenches rest on top of, and are connected to, the flooring units and the distribution ducts. Each trench extends transversely from an electrical power/communications closet to each duct. After the assembly has been completed, concrete is poured over the flooring units and the distribution ducts so as to be level with the tops of the trenches. Removable covers are kept on the trenches during the pouring of the concrete to prevent the concrete from entering the trenches.
Each trench has a power cell in which electrical cables are laid, as well as one or more additional non-power cells in which communication cables (e.g. telephone, analog signals) or data cables (e.g. computer, facsimile machines, digital signals) are laid. The power cells are physically separated and electrically insulated from the non-power cells. Similarly, each trench has separate power cells and non-power cells.
At each intersection of a trench with a duct, the power cells are in open communication with each other so that electrical power cables can be routed from the closet along the trench to and along a distribution duct. The non-power cells are also in open communication with each other so that the communication cables and/or the data cables can be routed from the closet along the trench to and along a distribution duct. The distribution ducts are typically spaced apart about 4 ft. center-to-center. Access to any one or all of the cables at any particular location along a distribution duct is typically obtained by drilling a single hole through the concrete floor into the duct, and by pulling the power/and or the communication and/or the data cables through the hole to a service fitting that is either elevated above the floor or mounted flush with the floor.
With the advent of the electronic office having more and more workstations per square foot of floor space, including computers, telephones, facsimile machines and analogous electronic equipment, the trenches have literally become clogged with cables. To help alleviate the congestion inside the trenches, local area network (LAN) support devices, also known as multiplexers, have been installed inside the distribution duct at strategically selected intersections with the trenches. This helps reduce the number of long, individual cable runs to the closet.
Many such multiplexers require a source of electrical power and, to that end, an electrical junction box is provided at each such strategic location where a multiplexer is to be installed. The junction box is tapped off the power cell in the distribution duct at the intersection, and extends physically into the trench.
With the ever-increasing demand for more and faster workstations, the multiplexers have increased in the number of their outputs and in size. The ever-physically-larger growing multiplexer in the distribution duct at a strategic intersection is beginning to encroach the trench. The junction box already in the trench, together with the multiplexer encroaching the trench, has decreased the capacity of the trench to carry more and more cables--a drawback which the present invention is intended to overcome.